The present invention relates to a fluid squirt gun for squirting fluid from a nozzle for removal of foreign matter stuck to a surface of a workpiece and the like.
This type of fluid squirt gun is generally formed such that a valve seat in a flow path is opened and closed with a valve element and that seating force in closing of the valve element is obtained by fluid pressure. Such a prior-art fluid squirt gun is advantageous in that a spring for valve closing is unnecessary because the valve element is closed by fluid pressure. However, if pressure of fluid becomes large, the seating force of the valve element on the valve seat becomes large. Moreover, the seating force of the valve element varies due to variations in the fluid pressure. If the fluid pressure varies, the valve element may be excessively pressed against the valve seat to reduce durability of the valve seat.
Furthermore, because the flow path of the fluid in the gun opened and closed with the valve element is not linear, a pressure loss is large and an effective cross-sectional area of the flow path is small due to bends of the flow path to thereby increase the pressure loss.
It is an object of the present invention to provide a fluid squirt gun in which a seating force for pressing a valve element against a valve seat can be obtained by repulsing force of a spring irrespective of pressure of fluid to thereby prevent the seating force from being affected by variations in fluid pressure and achieve a stable closed state of a valve and which has improved durability.
It is another object of the invention to provide a fluid squirt gun in which a flow path of fluid in a barrel is formed in a linear shape to eliminate bends and a reduction in an effective cross-sectional area of the flow path even in an opening/closing portion of the valve element to thereby suppress a pressure loss.
To achieve the above objects, a fluid squirt gun of the invention comprises, a linear flow path provided in a barrel, a nozzle at a tip end of the flow path, a valve seat provided in the flow path, a valve element disposed for movement in an axial direction of the flow path to open and close the valve seat, a spring for pressing the valve element in a valve-closing direction, and a trigger for opening and closing the valve element, wherein the valve element includes a forward pressure receiving face on which fluid in the flow path acts in a valve-opening direction in a closed state of a valve and a reverse pressure receiving face on which the fluid acts in the valve-closing direction in the closed state of the valve and both the pressure receiving faces have substantially equal pressure receiving areas.
In the fluid squirt gun having the above structure, because fluid pressure operating force acting on the valve element in the valve-closing direction and fluid pressure operating force acting on the valve element in the valve-opening direction in the closed state of the valve element are equal to each other, the seating force for bringing the valve element into contact with the valve seat can be obtained by only the repulsing force of the spring. Therefore, the seating force is not affected at all by variations in the fluid pressure, the stable closed state of the valve can be obtained, and problems such as reduction of durability of the valve seat and the valve element due to variations in the seating force are not caused. Furthermore, because the flow path of the fluid in the barrel is formed in the linear shape, there is not a bend of the flow path or a reduction in the effective cross-sectional area even in the opening/closing portion of the valve element and the pressure loss is not generated.
According to a concrete structural form of the invention, the valve element includes a received pressure adjusting portion for sliding in a sealed state in the flow path in a position upstream from the valve seat, a valve portion for opening and closing the valve seat from a down stream side, a stem connecting the valve portion and the received pressure adjusting portion, and a through hole provided in the received pressure adjusting portion to connect a flow path portion upstream from the received pressure adjusting portion and a flow path portion downstream from the received pressure adjusting portion and the forward pressure receiving face and the reverse pressure receiving face are formed such that fluid pressure operating force in the valve-closing direction and generated by the received pressure adjusting portion and fluid pressure operating force in the valve-opening direction and acting on the stem and the valve portion are equal to each other.
In this case, the received pressure adjusting portion is formed with a pressure receiving face facing an upstream side and a pressure receiving face facing a downstream side, the forward pressure receiving face is formed of the pressure receiving face of the received pressure adjusting portion facing the upstream side and pressure receiving faces of the stem and the valve portion, and the reverse pressure receiving face is formed of the pressure receiving face of the received pressure adjusting portion facing the downstream side.
According to a further concrete structure of the invention, the received pressure adjusting portion includes a small-diameter portion for forming the pressure receiving face facing the upstream side and a large-diameter portion for forming the pressure receiving face facing the downstream side. The small-diameter portion of the received pressure adjusting portion and the valve portion have substantially the same diameters. In the barrel, an operating chamber sealed from the flow path is provided around the flow path. A part of the received pressure adjusting portion of the valve element is disposed in the operating chamber and the trigger is in contact with the part.
According to another concrete structural form of the invention, the valve seat is in a disc shape, has an annular seat portion at an outer periphery of the valve seat, and disposed concentrically with the flow path in a central portion of the flow path. The valve element is in a hollow tubular shape, has small-diameter portions having inside diameters substantially the same as a seat diameter of the valve seat on axial opposite sides of the valve element and a large-diameter portion having an inside diameter larger than the seat diameter between the small-diameter portions, is disposed in such a position as to surround the valve seat to be movable in the axial direction of the flow path, has a valve portion formed of the small-diameter portion positioned downstream from the large-diameter portion and the forward pressure receiving face and the reverse pressure receiving face on an inner face of the large-diameter portion.
In the barrel, an operating chamber sealed from the flow path is provided around the flow path. A projecting portion formed on an outer periphery of the valve element is disposed in the operating chamber and the trigger and the spring are in contact with the projecting portion.